The present invention relates to a resilient material element intended to be subjected to compression forces in a given main direction and to be thus flattened between two of its ends, so that, considered in the direction from one at least of these ends inwards, it has at least one sudden increase of cross section, transversely to said main direction, whereby the stiffness of the element may increase in a proportion appreciably greater than the increase of said forces from the moment when the latter reach a given value.
In numerous applications, particularly in resilient material devices providing the suspension for internal combustion engines on the chassis of vehicles, it is necessary to obtain low stiffness (low modulus of elasticity) when the device is subjected to low force stresses, particularly under compression, and an appreciably higher stiffness from the moment when the stresses exceed a given value.
The reason for this requirement is that, for low amplitudes of the forces which are exerted on the device, good damping of the noises and the normal vibrations of the engine require a very low stiffness of the support. On the other hand, this low stiffness would become a hindrance if it existed for very high amplitudes of the compression forces, such as those which may occur when the vehicle passes over a pothole, or other sudden discontinuity of the roadway. In fact, in this case, the resilient support device would no longer fulfil its role as damper and coming into abutment would be fierce.
It is then the need to obtain progressive abutment even when the forces are considerable and sudden, closely related to shocks, which leads to constructing devices whose stiffness increases greatly when the compression forces which are exerted thereon increase.
Devices of this type are already known in which the resilient material element is formed by a rubber or elastomer block comprising cavities on the inside. These cavities confer on the block a relatively low modulus of elasticity for low forces, but the stiffness increases suddenly when, under the action of increasing forces, the block is compressed until the cavities are completely crushed.